The present invention generally relates to improvements in the field of non-destructive testing and failure analysis using pulsed ultrasonic energy. More particularly, the present invention concerns a device for performing acoustic micro imaging (“AMI”) operations that utilizes a balanced linear motor to move an acoustic transducer in at least one direction.
Various issued patents disclose AMI devices that utilize pulsed ultrasonic energy for purposes of non-destructive testing and failure analysis. For example, U.S. Pat. No. 4,781,067 discloses a balanced scanning mechanism. In the abstract of this patent, it is stated that the mechanism disclosed in the patent is used to drive a transducer of an acoustic microscope or other instrument rapidly back and forth along a linear path comprising the X portion of an X-Y scan pattern. The abstract also states that the transducer is mounted on a first carriage, and that a counterweight may be mounted on a second carriage, with the total mass of each carriage and the contents thereon being equal. The abstract further states that drive belts are connected to both carriages to drive them reciprocally along the X axis with accelerations and velocities that are equal in amplitude but opposite in direction. Conventional motors and pulleys are used to drive the belts. The content of this patent is incorporated by reference into this application as if fully set forth herein.
As another example, U.S. Pat. No. 6,357,136 issued on Mar. 19, 2002, and is entitled scanning acoustic microscope system and method for handling small parts. The abstract of this patent states that the use of the invention prevents the dislodging of small, loosely held parts from trays during inspection or during drying. The content of this patent is incorporated by reference into this application as if fully set forth herein.
A further example is U.S. Pat. No. 6,880,387, which issued on Apr. 19, 2005, and which is entitled acoustic micro imaging method providing improved information derivation and visualization. The abstract of this patent states that an acoustic image of a sample is derived, and then visual superposition of one or more additional images is obtained. The content of this patent is incorporated by reference into this application as if fully set forth herein.
A still further example is U.S. Pat. No. 6,890,302, which issued on May 10, 2005, and which is entitled frequency domain processing of scanning acoustic micro imaging signals. In the abstract of this patent, it is stated that a time domain signal, which is representative of acoustic impedance features in a sample, is obtained, and then is converted to the frequency domain. The abstract also states that the frequency domain signal can be modified, and then converted back to a time domain signal. The content of this patent is incorporated by reference into this application as if fully set forth herein.
An additional example is U.S. Pat. No. 6,895,820, which issued on May 24, 2005, and which discloses an acoustic micro imaging method and apparatus for capturing 4D acoustic reflection signals. The abstract of the patent states that an ultrasonic transducer is utilized to interrogate a sample at three dimensionally varied locations within the sample, with an in-focus A-scan being produced for each location interrogated. The content of this patent is incorporated by reference into this application as if fully set forth herein.
A further example is U.S. Pat. No. 6,981,417, which issued on Jan. 3, 2006, and which discloses a scanning acoustic micro imaging method and apparatus for non-rectangularly bounded fields. The abstract of this patent states that a stage system is commanded so that an ultrasonic probe interrogates a non-rectangularly bounded space on the sample surface and/or within the volume of the sample. The patent also states that FIGS. 21-29 schematically illustrate various 2D and 3D scanning modes and techniques which may be employed in connection with the invention disclosed in the patent. The content of this patent is incorporated by reference into this application as if fully set forth herein.
Other patents that disclose various AMI devices include U.S. Pat. Nos. 6,460,414, 5,684,252, 5,600,068, 4,866,986 and 4,518,992. The content of these patents are incorporated by reference into this application as if fully set forth herein.
A number of published patent applications disclose various other AMI devices. For example, US Published Patent Application Nos. 20030045768 and 20040048111 are entitled “ultrasonic probe for operation under microscope.” Paragraph 169 of both publications state that “an advancing/withdrawing mechanism” for a “reflector 61” may be constructed with “a linear motor 62 and a switch 63.” The content of these publications is incorporated by reference into this application as if fully set forth herein.
As an additional example, U.S. Patent Publication No. 20040173024 is entitled “method and apparatus for temperature controlled ultrasonic inspection.” This publication states that the “relative positions of the object under inspection 130 and the ultrasonic transducer 102 are adjusted along a scan-line by action of a first position controller 134 (such as linear-motor or a stepper-motor under control of the system computer 106) that moves the transducer along a track 136.” The content of this publication is incorporated by reference into this application as if fully set forth herein.
In August of 2001, a company called Sonix issued a press release which describes its scanning acoustic microscope model no. UHR-2001. The press release states that the UHR-2100 microscope includes a 0.5 micron encoder on the scan axis, an improved ball screw for greater positioning accuracy, a linear servo motor, and a transducer that is directly coupled to a servo forcer.
Currently available AMI devices having a linear motor, such as those described above, are significantly limited in use. In order for useful data to be obtained in an AMI operation, vibration that is caused when the transducer assembly is accelerated or decelerated must be kept below a certain ceiling amount. For example, the linear motors used in the above-referenced devices must be subject to not more than 0.1 G when accelerated or decelerated. As a result of this, the linear motors can be operated at top speed only about no more than 40% of the time. When the linear motors are operated at such low efficiencies, the time that is required to scan a particular sample (e.g., an integrated circuit package) is necessarily substantially increased well beyond what would be possible if the motor were operated at a higher efficiency rating. This disadvantage is compounded when the AMI device is used to perform failure analyses on trays of samples in commercial applications, which leads to an undesirable increase in costs.